Can this M96 crankshaft be saved?

The local Porsche Indy was convinced the problem was IMS -even when I told him it had just been replaced about 2000miles earlier(LN). I walked-quickly! Anyway here's what was causing the noise.The #5 journal is scored-see pic. Obviously the bearing shells have even more damage but are they did not disintegrate. Strangely the bearing shells appear to have rotated in the con rod big end because they are scored on both sides. The scoring fails the crude fingernail test. I'm sure the machine shop will want to 'try' to save the crankshaft. On a regular engine I would take a chance but the M96 rebuild and re-install is a daunting & expensive task if it turns out to be futile. For that reason, I would be very grateful for advice on how to proceed with this project and what to ask a machinist. For background, the engine has 90k miles, several upgrades (LN filter mod,new IMS to name a few) oil was very clean.No signs of any dirt inside the engine,no sludge and obviously had not been opened since new except for the minor IMS bearing job. Only two other defects found so far -one chain ramp is pitted but nothing severe. 22 of the lifters had jammed solid ! Overall ,the engine is in remarkably good condition - except for #5 con rod bearing and the lifters.

I would drive it down to Marine Crankshaft in Santa Ana and ask the owner's opinion. Obviously the indy you mentioned is not to be trusted....

The subject of crankshaft resurrection has come up before and without doing a search to confirm my memory I do not think it is a recommended course of action. Oversize bearings are not available -- this was circa 2011/2012 and maybe (maybe) this has changed -- so the crank pin or main bearing can't be ground undersized to clean it up -- assuming this wouldn't compromise the surface hardening/heat treatment -- and building up the worn crank pins or mains with say an application of hard chroming and regrinding to stock size has not proved to be successful either. Other crank main/pin bearing build up/restoration techniques such as welding are likewise not advised. I seem to recall the above was courtesy of Jake Raby in response to a posting by someone else, while I was the one who offered up the hard chrome suggestion as in the machine shop many a worn bearing journal was repaired with a proper hard chrome application then regrinding to size, but Jake R. shot this down as I recall. However, you can check ads in Excellence and Panorama for shops specializing in engine rebuilds/repairs and learn if any offer crankshaft rebuilding services. Things may have changed. You can even check with Jake Raby but I seem to recall he does not sell parts only complete rebuilt engines. But check anyhow. Maybe he knows someone that rebuilds cranks for these engines.

Thank you both for the wisdom. I had thought of asking John Edwards at Costa Mesa R&D. He has a good reputation for honesty & competence on the air-cooled engines . I'll inform the Forum of the outcome because good used crankshafts are hard+expensive($800+ -) to find.

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Someone going by the name "acracer" posted a while back in a thread some details on what was supposed to be 996 crankshaft dimensions and added "with the amount of engines we do.......info can be shared, as we're in NYC and busy." Here's a link the thread: https://rennlist.com/forums/996-foru...aft-specs.html The "acracer" post I referred to above is #8. You might send him an email and ask him about the crankshaft.

Interesting link-that is helpful.Thank you. I'll call Gleason and ask who has their machines nearby. http://www.gleasonengineering.com/ I note one celebrated contributor advises crack testing because 50% of cranks he inspects are cracked. Wow! that is a horrific statistic.

In post #9 he states or am I missing something? Or maybe you figure that he found the 996 specs and didn't post?

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I posted the link to get the OP to "acracer" so he could send him a PM about shop acracer mentioned (but didn't name) and if it does crank rebuilding/refinishing. The crank dimensions I knew were no good for as you pointed out in the following post acracer said the dimensions were for a 964 crank. AFAIK, and I've kept my eye out for them, there have not been any 996 crankshaft dimensions published. I put out some feelers to see if I could get some from my tech contacts but the info was not right at hand -- the info was supplied -- if it was supplied at all and I'm not sure it was or won't be sure until I actually see it -- almost prior to the 996 launch and this info tends to settle to the bottom of the sizable stack of printed material a tech ends up with over the years -- and did not pursue it. Were I seriously considering rebuilding a 996 (or in my case a 986) engine I might feel more driven to get my hands on this info but I'm not in the engine rebuilding mode and so I didn't push the techs for this.

Macaster, relax, you've already done more than your share to help Rennlisters ! The older the M96 engined cars get ,the more often this subject will come up.The less satisfactory the solution to fundamental problems like cranks, blocks etc - the lower the value of the cars. The honest contributions of experts who explain on this Forum that 50% of the crankshafts that come in have cracks, the worse it gets. We may love these cars but if they don't run -what value do they have? We have seen this happen to cars like the 928, Jaguar XJS. Arguably ,the parts/repair situation for their engines is stronger than for the M96 cars. So I suggest it is in our collective interest to pool resources here to save the cars.In the case of the XJS -it was saved by Forums like this - particularly Jag-Lovers.. We could do the same.I'll make a minor contribution by posting here the outcome of the crankshaft saving attempt.

First things first, have the crank magna flux tested for cracks. If it passes then worry about restoring the journal. If it does not, then journal restoration doesn't matter. Cranks with spun bearings generally crack during the failure. I have developed a means of journal restoration, but it requires many processes and an altered bearing to be used. After all those efforts are done the crank must be Ion Nitrided to restore surface hardness, as the factory hardness only penetrates .003" into the crankshaft. You will not find the M96 crank dimensions posted anywhere.

I had my crank welded and re grinded when my 5th rod bearing went bad. I had to change the rod allso. I found used from England, I think it was 100� shipped. Driven over 50k km's after that. I allso had cyliders that were too much out of round. (supposedly) At 10k km oil change interval, no need to add oil. Oil level drops one notch in the dash gauge. No fouled plugs etc.... I allso ported my cylinder heads and used wet sandpaper to clean the aluminium debries from cyl 5 Still running strong

Speed in Finland, Kiitos paljon ! So yours failed on number 5 also-interesting. I wonder why number 5 ? Congratulations on your repair.It is encouraging to read that someone tried a risky repair and succeeded.I carefully follow the comments of Jake Raby above & I wrote "I note one celebrated contributor advises crack testing because 50% of cranks he inspects are cracked. Wow! that is a horrific statistic."

Your welcome, ole hyv� When I took my engine apart I found no solid proof why the bearing failed. Failure started from mainbearing, and the debries from that took out the rodbearing My theory was, that engine had oil starvation on nurburgring. I didn't have the oil filled up to max and it's possible the the failure began there. Drove about 4k km after the road trip, before the bearing went. Other theory was that allmost all the oiljets, that are in the crank cradel, was stuck open. This might cause poor oil pressure on the crank when engine is hot and idling. If I remember right, logray found allso stuck oiljets in his engine when he did 3,6 conversion.

Stuck oil jets -Hmmmm, thanks I'll test them too. At least you had the fun of a run around the 'ring before yours died.Mine was not so exciting ! One mod I plan on doing to mine(if I can save the engine) is the oil/water heat exchanger delete. Apparently that increases oil pressure somewhat.Yes, I know there are lots of other mods to do but that seems to be one that is often misunderstood. Interesting to note since you are from Finland that many of the Boxsters were made by Valmet in Finland -along with the Saabs and tractors ! An interesting company.

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These engines do not suffer from low oil pressure unless there's a real problem. The oil/water heat exchanger helps warm the oil up when the engine is cold which reduces cold wear and helps keep the oil from getting too hot when the engine is pushed which works to keep wear when hot at bay. Remember the oil is in contact with the hottest parts of the engine and plays an important cooling function. What you gain in oil pressure with the removal of the oil/water heat exchanger you'll like lose and then some when the oil gets much hotter than it would otherwise.

Would be nice if it actually worked as it's designed. The heat exchanger does a great job of warming the oil when cold, but a marginal job of cooling it when its hot. My data logs of this are staggering in high ambient temps and on the track the arrangement isn't effective after around 83*F generally. The crankshaft oil pasages are also poorly positioned for high speed oil delivery to the rod journals, which is the major defect that leads to spun bearings with these engines. Bet you never heard that one before.

The Laminova heat exchangers on Ford/Jaguar Duratech engines have the same problem and are removed to fit real oil coolers . Not surprisingly LN sell a a heat exchanger delete for the M96.

Back to Crankshafts !And the cause of the bearing damage. Mine has a spun bearing in #5 and rear main bearing damage. But why? Interesting on the rear main bearing damage - it was slight and it did not 'spin'. The Machinist who has done many M96 engines said he guessed the DMF was 'bad'. Indeed it was.I posted about this a month ago. But it was not very far outside spec(according to the PO who had done an IMS job) . The Machinist loves old DMFs - brings him new customers ! My DMF was original,now at 90k miles. He advises balancing the new DMF with pressure plate attached and mark it to avoid reassembly errors. He commented adversely about out of balance/worn DMF+clutch assy and the damage it causes to bearings/cranks and even the c/s carrier. So be careful to measure the 'play' on the DMF correctly. The spec is easy to misread as an allowable movement clockwise or ccw.It isn't.The spec is for total movement -the sum of both cw & ccw. I posted a photo of this highlighted in white marker paint previously.Yes a DMF is expensive -$350 but an engine rebuild is......I was tempted to fit a regular flywheel+sprung clutch but deterred by advice of the experts here. It just seems technically risky to have so much poorly balanced weight hanging past the end of such a small main bearing.... He'll get a used,good rod for #5 and repair the mess. Presumably the oil supply to #5 was plugged by debris from the main ? The LN filter did not catch everything unfortunately? And I still don't know why 22 of the 24 hydraulic tappets in the lifters had jammed solid. Still no confirmation if the revised lifter part number 996.105.041. 72 is modified to address this issue or not.For reference the old lifter # is 996.105.041. 50 Confusingly the OEM supplier(INA in Germany) does not have a revised part number - it is unchanged from 1997 to date : INA420 0049 10 Hopefully I'll start rebuilding the engine in a week or so.

So why do the failures occur in the exact same manner when a single mass flywheel is fitted? What leads to the connecting rod bearing failure isn't rooted with the DMF. Give me a couple of days and I';ll be on a plane heading to instruct one of my classes in San Fran and I'll take the time to explain the dynamic of this failure. We have caught many of these during failure and of course we've seen hundreds post failure and as a researcher I document all of those things. Its very easy to see what actually occurs. Thats how we keep it from recurring with our engines.

"So why do the failures occur in the exact same manner when a single mass flywheel is fitted" I am unqualified to respond. And I doubt I am even qualified to attend the seminar even though I live nearby, so just a guess : 1.perhaps the bearing is too small even for an unbalanced lighter mass flywheel ? 2. A helpful fellow on this Forum also said that a regular/lightweight flywheel fails to absorb harmonic imbalance from elsewhere in the drive-train - that the DMF does absorb . So the solution may indeed be to balance ..but what ? just the DMF plus pressure plate ?

Because the flywheel is not the root of the problem.

Jake you are a busy guy - building an R&D extension ,flying around like a rock star - it is impressive but instead of all this sturm und drang ,couldn't you just offer a video conference so we could all pay/sign up and share the knowledge ? After all, some of us have contributed a little to your meticulous research :-). And please, please publish your book! My engine is in pieces and I have no reliable resource to put it back together intelligently -I am waiting for your book!

You can attend my WTI class this weekend then my hands on class next month..

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It could be the crank damage is collateral damage arising from an internal oil leak caused by 22 collapsed lifters. Collapsed they could offer less resistance to oil flowing from the oil holes that are intended to lube the lifter bucket in its bore and feed high pressure oil to the zero lash aduster. Thus the top end develops an oil leak that robs the bottom end of oil. It doesn't take a rod or main bearing long at all to manifest all sorts of problems from inadequate oiling. (Oh, and I know when a lifter collapses it does not cause the lifter to get smaller in diameter but it does allow the lifter bucket to pull away from the cam and sit lower or make that further down into the lifter bore. Even if this doesn't uncover the oil hole in the lifter bore it does offer less resistance to the oil from the oil and this constitutes an internal oil leak.)

The lifter theory is interesting but there was no indication of reduced oil pressure-even when the rod bearing started banging. I am beginning to think a 'real' oil pressure gauge is required -&/or a Scangauge/Ultragauge

The oil pressure to the rod bearings is partly generated by the centrifugal force of the crankshaft. Think about this and then I'll let you piece the puzzle together.

I think I shall ask the Mod. to rename you "Riddler Raby" :-). I feel bifrucated -if you follow Batman. By the time I save up for your Costa Mesa class and complete my rebuild, I shall have some riddles for you too! I worked in Prod Dvpt for truck diesel engines so have a rusty, basic understanding the role of the crankshaft creating oil pressure through the wedge/rotation effect between the bearing shells. When the clearance between the shells increases too much &/or the oil supply to the bearings is obstructed ,the crankshaft can no longer pump pressurized oil. Only the oil pump remains for that duty and it is inadequate alone because it creates flow, not pressure. The pump collects unfiltered oil so distributes debris.Then the cascade of oil pressure-related failures starts -including 22 of my lifters. Am I even close?

You are thinking too hard… So, what if the engine oil loses film strength and due to this and inadequate factory running clearance this created main bearing wear that damaged the rear main bearing?? Would that debris laden oil not be centrifugally delivered to the rod bearing journals for cylinders 3 and 6? If that happened, what would happen?

If that happened, what would happen? Weepy-weepy.

Part of the answer may be here: http://lnengineering.com/resources/2...m96m97-engine/ and in this oil flow diagram: http://tunersmotorsports.com/wp-cont...IAGRAM-001.jpg Come on Rennlisters -help me keep up with the Riddler here!

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It's called an opportunity… To buy a real hand built, updated engine :-) BTW- The oil flow chart that was linked is not accurate. Its not a system configuration. Its wrong in the factory manual, like so many other things.

^^^ That engine was not rebuildable.

The crankshaft mentioned by the OP was saved ! No cracks fortunately.

It probably didn't matter anyway. What did the owner end up doing? Its amazing how many M96 NA's end up as scrap metal. This is pretty much unheard of with any other engine designed. Its really depressing.

That engine is being rebuilt with the 'saved' (= very skillfully repaired and tested) crankshaft

What proces was used to "save" it?

Used a specialist crankshaft recon company that does lots of Porsche cranks.(Dave) http://www.marinecrankshaftinc.com/outboard.html For the details I would suggest discussion with an expert(I am unqualified !) Check all dimensions Magnaflux Metal deposition rough machining back to size chamfer rod oil holes balance final machining /polishing lots of cleaning

Thanks for the info. I might have to use them.

I suppose it can be welded and reground like any other forged crank, right? If its not forged, I just lost what little love I had left for the M96 NA.

It is forged but that doesn't help much if it gets cracked - and that happens because of the very narrow rear main bearing and the huge weight(DMF) dangling off the rear of the crankshaft of the manual trans cars.

Maybe Jake re-enforces the main webbing in this area during his secret process?